Wheels for motor vehicles, such as for example passenger motor vehicles, and in particular the main members thereof, are commonly produced from steel. Here, the main members are formed for example as areal wheel discs. It is furthermore known, for example for improved cooling or for a weight reduction, for a circle of holes to be provided in the main member. Since such wheels however often do not meet the aesthetic demands of the customers, use may be made of wheel caps or decorative covers composed for example of plastic, which substantially completely cover the main member and permit a flexible design. However, these measures often also do not meet the aesthetic demands, because the wheel caps are generally recognized as such.
By contrast, a better visual impression can be afforded by so-called light-metal wheel rims, in the case of which the wheel-rim ring and the main member are forged or cast in one piece or in multiple pieces. However, for this purpose, increased production outlay and cost expenditure in comparison with conventional steel rims must be accepted. Furthermore, corrosion resistance is often a problem even in the event of light damage to such wheels.
Furthermore, so-called steel structure wheels are known. Here, the main member can be reduced such that the main member can be of a spoke-type design. Here, too, to achieve an appealing appearance and adequate design flexibility, use is made of plastics wheel caps. It is however a particular disadvantage that, owing to the reduced main member with spoke structure, it is necessary, in order to ensure adequate stiffness and strength, to accept a weight which is up to 25% higher than that of a conventional steel type of construction. This arises in particular from the required large wall thickness of the main member. The large wall thicknesses furthermore necessitate high deformation forces during the production process, and are restricted in terms of their freedom with regard to shaping.
In view of this problem, vehicle wheels as mentioned in the introduction are proposed in the prior art of DE 101 27 639 A1. Accordingly, a wheel having a wheel-rim ring and a main member is provided with a covering shell in order to avoid large wall thicknesses. Here, the single-piece covering shell has substantially the shape of the main member and, like the main member, has openings, such that the covering shell can be attached together with the main member to the hub of the motor vehicle by way of a screw connection. For this purpose, the covering shell lies on the screw-on flange of the main member in the region of the openings. By means of the common connection of covering shell and main member to the vehicle hub, adequate stiffness of the wheel is ensured.
It has been found that, by means of such a construction, it is duly possible to achieve a lower weight with increased design freedom. However, it has been found that, in particular during operation, relative movements between the covering shell and the main member may occur, which can have an adverse effect on the screw connections and, in association with this, on a secure screw seat and on the bracing force of the screw. Furthermore, it is also desirable to achieve additional weight savings.